Track and field is a sport in which athletes compete in running, jumping, and throwing events. In an event known as the pole vault, an athlete uses a pole to jump over a cross bar. The pole vault originated in Europe where men used a wooden pole to cross over canals filled with water. By the late 1800s, the pole vault had been added as an event at track and field competitions. The early pole vaulters used a bamboo pole with a sharp point on the end and competed on a grassy surface. In the first modern Olympics in 1896, the winning vault was a height of ten and one-half feet (about 3.2 meters). In the following century, techniques and equipment improved so dramatically that the current record is over twenty feet (over 6.1 meters).
One of the changes in equipment that occurred in the past century was the use of a vault box for planting the pole. A vault box (also known as a planting box) is a recess permanently mounted at the end of a runway and a short distance in front of the standards and cross bar. When using a vault box, the pole vaulter runs down the runway holding the pole in a horizontal position, plants the distal end of the pole into the vault box, and then elevates.
Another one of the changes that occurred in the past century was the use of fiberglass for the pole. Compared to bamboo poles, fiberglass poles are much lighter in weight and have a much greater ability to convert energy. In terms of physics, the vaulting pole converts the kinetic energy of the running vaulter into potential energy that is used to overcome the force of gravity. There is no limit to the length of the pole. The best male vaulters use a pole that is about seventeen feet (about 5.2 meters) long while high school girls may use a pole that is only about twelve feet long (about 3.7 meters).
FIG. 1 illustrates a person 10 performing a pole vault. The vaulter holds onto a pole 20 that has been planted into a vault box 30 at the end of a runway 40. The vaulter is attempting to clear a cross bar 50 elevated between two standards 60. At the moment shown, the pole is bent at the maximum angle and is about to straighten out to propel the vaulter upward over the cross bar. For brevity, masculine pronouns are occasionally used herein.
FIG. 2 is a more detailed view of the vault box with the distal end of a pole shown in phantom lines. The size and shape of the vault box has been standardized by the various track and field governing bodies. The vault box has a length of about 43 inches (about 110 cm), a width of about 24 inches (about 60 cm) at the front, a width of about 16 inches (about 40 cm) at the rear, and a maximum depth of about 8 inches (about 20 cm). The vault box contains an outwardly sloping rear wall 31 (also known as the stop board), an outwardly sloping left side wall 32, an outwardly sloping right side wall 33, and a bottom surface 34 that slopes downwardly from front to rear. The outward slope of the side and rear walls is about 105 degrees. The vault box has two back corners, one where the rear wall, left side wall, and bottom surface meet and one where the rear wall, right side wall, and bottom surface meet. The side walls converge from front to rear at the top (along ground level) and converge from front to rear at the bottom even more than at the top. The minimum distance between them at the lowest point of the bottom is about 6 inches (about 15 cm). During the vault, the distal end of the pole moves to one of the two back corners and bends outwardly toward the other back corner as shown.
After completing the jump, the vaulter lands in a cushioned landing area on the far side of the cross bar. Early landing areas were pits filled with sawdust or sand. As the height of the jump increased, advances were made to the landing areas. A modern landing area typically consists of multiple foam blocks secured together. The foam blocks have a thickness (height) of several feet (one or more meters) so the distance from the cross bar to the top of the cushion is reduced. The landing cushion is omitted in FIG. 1 for simplicity and clarity.
Despite the use of cushioned landing areas, injuries continue to occur during pole vaulting. A major cause of injuries is the failure of the vaulter to land on the cushion at the far side of the cross bar. If the vaulter fails to place the pole into the vault box or fails to properly perform the vault, he may elevate in the wrong place or at the wrong angle, and drop back down at a place other than the landing area.
Serious injuries often occur when the vaulter drops back directly over the vault box and lands in a supine position (facing upwards). In some instances, the vaulter falls into the vault box in position that is roughly parallel to the vault box (i.e., with his spine aligned with the longitudinal axis of the vault box) as shown in FIG. 3. Severe injuries occur when the head hits the bottom of the vault box. In other instances, the vaulter falls onto the vault box in a transverse position (i.e., with his spine at an angle to the longitudinal axis of the vault box, with his shoulders at the edge of the vault box, and with his head directly over the vault box) as shown in FIG. 4. As the back and shoulders make impact, the head is thrown backward and downward into the recess. If the head is positioned over a shallow part of the recess, the head will make contact before the neck breaks and severe head trauma results. If the head is positioned over a deeper part of the recess, the neck may break before the head makes contact.
Cushioned collars that surround the vault box are commonly used. For example, a relatively thin cushioned safety collar that surrounds the sides and rear of the vault box is commercially available from Gill Athletics, Inc. of Champaign, Ill. These collars are ineffective at preventing the injuries described above when the vaulter lands into the vault box because they contain upper openings that are the same size as, or slightly larger than, the upper perimeter of the vault box. As another example, Smith, U.S. Pat. No. 4,443,009, Apr. 17, 1984, discloses a relatively thick cushion that surrounds the vault box. The recess of the cushion angles outwardly from the vault box so it does not interfere with the bending of the pole during the vault. The Smith cushion is also ineffective at preventing the injuries described above because the size of its upper opening is much larger than that of the vault box.
Narrowing the vault box to reduce the catastrophic injuries described above in which the vaulter lands directly over the vault box has not been proposed. The primary reason narrowing has not been proposed is presumably because it would increase the likelihood of other injuries resulting from a failure to plant the pole into the vault box.
Accordingly, a demand exists for a vault box safety cushion that reduces the risk of catastrophic injury if the pole vaulter lands directly onto the vault box, but does not make it more difficult for the pole vaulter to plant the pole into the vault box.